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Forum:	Mercury - Gemini - Apollo
Topic:	Gemini hatches and emergency egress

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Your Reply: HTML is ON UBB Code is ON Smilies Legend	[QUOTE]Originally posted by NavyPilot: [B]Unfortunately, this film does not include the actual hatch actuation -- can't seem to find that anywhere, yet. But at ~1+02, you can see the left hatch rebounding and resonating from the emergency opening force, which was done via pyro (versus spring or compressed gas or other). <center><iframe width="400" height="225" src="https://www.youtube.com/embed/JXmta6-6bPo" title="YouTube video player" frameborder="0" allow="accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture" allowfullscreen></iframe></center>[/B][/QUOTE]
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<table border=0 cellpadding=0 cellspacing=0 width="600"><TR><td bgcolor="#000000"><TABLE BORDER=0 cellpadding=4 border=0 cellspacing=1 WIDTH="100%"><TR bgcolor="#660000"><TD COLSPAN=2><CENTER>T O P I C     R E V I E W</CENTER></TD></TR><TR bgcolor="#494949"><TD valign=top>Paul78zephyr</TD><TD>I was recently re-watching an oral history video with Glynn Lunney from 1998 in which he was commenting on the circumstances of the Apollo 1 fire and states that the Gemini capsule was also pressurized to 14 psi with pure oxygen during testing. This made me wonder if a fire or other emergency had broken out during a pad test similarly to Apollo 1 if the Gemini crew could have quickly opened their respective hatches and egressed? Was this something they trained for?I don't know much about the Gemini hatch other than it was hinged and swung outward. The Apollo Block II hatch had a special "quick operating" mechanism to allow a single crew member to rapidly release the latches - did the Gemini hatches have similar features?</TD></TR><TR bgcolor="#333333"><TD valign=top>oly</TD><TD>Gemini was equipped with an ejection seat system that jettisoned the hatches. Theoretically, it was capable of a Zero-Zero ejection through to a high-velocity ejection up to 100,000 feet altitude. </TD></TR><TR bgcolor="#494949"><TD valign=top>NavyPilot</TD><TD>Unfortunately, this film does not include the actual hatch actuation -- can't seem to find that anywhere, yet.But at ~1+02, you can see the left hatch rebounding and resonating from the emergency opening force, which was done via pyro (versus spring or compressed gas or other).<center><iframe width="400" height="225" src="https://www.youtube.com/embed/JXmta6-6bPo" title="YouTube video player" frameborder="0" allow="accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture" allowfullscreen>

NavyPilot

Go-to reference: Development and Qualification of Gemini Escape System.

space1

The responses so far discuss Gemini seat ejection. But that would be an extreme response to a cabin fire. And it would not work at all if the pad white room were still in place.

The Gemini hatch was very different from the original Block I Apollo hatch. The Apollo hatch was in two pieces, with the inner hatch opening inward by being completely removed from the hatch sill. Then the outer hatch would be hinged open.

The Gemini hatch could quickly be opened by cranking on the inner hatch handle for a few strokes, unlocking the latches. The hatch could then be pushed open on its hinges. (If the cabin were under pressure, the hatch would readily open (slightly) with the first crank of the handle, enough to release the excessive cabin pressure. Also, at no time would the Gemini hatch be released from its hinges.)

The astronauts and ground crew were trained for quickly egressing the Gemini. I don't know offhand if a cabin fire was particularly considered. Fire resistant materials were commonly used, such as Nomex for the suit. And the fabric on the cabin walls was treated with a fire retardant. But no special consideration was given to the effects of a pure oxygen atmosphere on a cabin fire.

David C

Back to the ground level ejection scenario. Tom Stafford has commented several times that he wasn’t convinced. Here’s the version in his oral history:

...what we would have seen, had we had to do that, would have been two Roman candles going out, because we were 15 or 16 psi, pure oxygen, soaking in that for an hour and a half.

The tests were not conducted under those conditions.

space1

Regarding Stafford's ejection comments, he was not even referring to a fire in the cockpit. He was saying that a standard Gemini ejection scenario would ignite the pure oxygen in the cabin and cause their oxygen-soaked suits to catch fire.

David C

Correct.

Jim Behling

quote:
Originally posted by space1:
He was saying that a standard Gemini ejection scenario would ignite the pure oxygen in the cabin and cause their oxygen-soaked suits to catch fire.

Which really would not happen and is a myth regardless what the astronauts said.*

Oxygen does not burn.
The seats and astronauts would be moving too fast for anything to ignite.
The suit outer layer was nomex which does not burn
The seats are already outside mixing with air before the motor starts.

* astronaut said they almost crashed on the moon in Apollo 10.

space1

Jim, I think you are most likely right. The problem (as you know) is that the Nomex, and other fabrics including parachutes, would have been soaking in pure oxygen for over an hour. When fabrics for Apollo were being tested after the fire, Nomex was not chosen for use. So it is not ideal under these conditions.

The question would be whether the ignition source would have had an effect on those materials as they were moving through the air. Timing of ignition, oxygen density as the hatches were opened, and other factors would determine the outcome. I think the ejection would have been fine. But we'll never know for sure.

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